Because Google gives out such little information about the internal workings of its algorithms, it's nearly impossible to say with certainty what issues webmasters can expect to face in 2013. Digital marketers failed to predict the widespread changes that would result from 2011's Panda update, just as they couldn't foresee the scope of the 2012 Penguin change.

Google typically does about 200 algorithm updates each year, but there's no way to know if another Panda or Penguin is in store.

But based on the changes we have seen recently, it's possible to make a few predictions about how the field of search engine optimization (SEO) could change during the coming year.

The Issues
A few fundamental shifts have occurred recently that will likely continue throughout 2013:

• Google's perpetual goal is to rid its results pages of spam. While the Penguin update took major steps in the right direction, this series of changes revealed a few new loopholes that allowed webmasters with low-quality pages to sneak into the natural search results. Expect further refinements of the Penguin update or an entirely new algorithm change, as Google continues its battle against spam.• Link building continues to become more difficult. As Google's algorithm updates invalidate popular linking schemes, the process of finding and securing backlinks for search engine optimization grows more challenging. As a result, it would be more appropriate to call the techniques that will work best in 2013 "link earning," rather than "link building."• Mobile internet usage grows, changing the scope of required SEO activities. With predictions that mobile internet usage will account for as much as half of all web traffic by 2014, it's imperative that companies implement mobile SEO best practices for their websites.

The Players
Although Google's changes are made behind closed doors, there are a few SEO industry insiders to follow for the early word on important new updates:

• Matt Cutts: You'll want to give any updates that come from the head of Google's Webspam team and the company's unofficial spokesperson extra consideration. Subscribe to his personal blog and pay special attention to his Twitter feed, for what Cutts calls "weather updates" -- messages that indicate new algorithm changes and that data refreshes are being released.• Danny Sullivan: The editor-in-chief of Search Engine Land is one of the rare people in the SEO industry who is often able to get clarifying responses from official Google spokespeople. I recommend following his updates on the Search Engine Land website and his Twitter account.• Rand Fishkin: The founder and CEO of Seattle-based SEO and social monitoring service SEOMoz is recognized as a member of the SEO world's "in crowd." To stay up-to-date on changes in the industry, follow the general posts on the SEOMoz blog, along with Fishkin's personal blog and Twitter account, which offer additional insights into the latest SEO news.

Predictions
Despite Google's secrecy, I'm comfortable making a few predictions about the relative importance of certain elements in the field of digital marketing. Specifically, I believe:

• 'Structured data' will play an increasingly important role in SEO. Structured data, or "microdata," is a special mark up language that websites can use to provide additional information about their content to the search engines. Given that Google has relatively few indicators to objectively assess quality and given how much it has been pushing the adoption of this system, I believe schema.org microdata and other forms of structured mark up will become even more important to website performance in the natural search results. • Good content marketing will become a more accessible path to website success. To be clear, "good" content marketing doesn't involve spamming sites with fake guest posts or distributing infographics simply because they're popular. Instead, valuable content on topics readers care about is what will help websites increase their inbound backlinks, brand reputation and referral traffic naturally. This will lead to success in the search engine results with much less effort than traditional SEO techniques.• Data-driven marketing techniques will drive out intuitive promotions. "Big data" was one of the hottest digital marketing buzzwords in 2012. Because the amount of information marketers have access to is only going to increase, it's wise to assume that data-driven decisions will become even more important to marketers this year.